The balancing shafts which are known to be used in internal combustion engines to partially or completely compensate for free inertial forces and/or moments of inertia are usually produced from cast or forged blanks. Known ways of supporting the balancing shaft in the internal combustion engine include not only sliding support but also rolling support or combined sliding/rolling support, in which case the raceway for the rolling bodies is formed either by an inner ring of the rolling bearing mounted on the bearing journal or, as is provided in the case of the present invention, directly by the outer lateral surface of the bearing journal.
However, the supporting method mentioned last may be disadvantageous in the case of a drop-forged balancing shaft because that point of the bearing journal which is subjected to the greatest loading and over which rolling bodies permanently roll is situated in the unbalance plane on the mass center of gravity side and the unbalance plane, as has been customary to date, coincides with the parting plane of the forging die. Although a parting plane of this type offers considerable advantages not only in terms of the then comparatively small outlay for producing the die halves but also in terms of the tool forces to be supported during the forging process owing to the fact that the balancing shaft is substantially symmetrical with respect to its unbalance plane, it is possible that the material fibers of the balancing shaft will flow together at that point of the bearing journal which is subjected to the greatest loading, and this is not suitable in terms of stress. Because the fibers are interrupted by the parting plane and are not homogeneously joined at that point, impurities included in the material may be transported onto the surface of the bearing journal as the balancing shaft is being forged and material simultaneously flows from the inside outward in the region of the loading zone. These impurities may then represent the starting point for premature fatigue damage on that spot of the raceway for the rolling bearing, which is subjected to the greatest loading.